The invention relates to an extrusion method which uses an extrusion device comprising a nozzle such that the extrusion device comprises means for supplying at least two different materials through the nozzle, and a product is produced by the nozzle, the product comprising at least two different materials whose relative proportion varies in an end product, the nozzle comprising at least two nozzle chambers such that the material flowing through a first nozzle chamber forms an outer part of the product and the material flowing through a second nozzle chamber forms an inner part of the product.
The invention further relates to an extrusion device comprising a nozzle and means for extruding at least two different materials through the nozzle, the nozzle comprising at least two nozzle chambers such that the material flowing through the first nozzle chamber forms an outer part of a product to be produced and the material flowing through the second nozzle chamber forms an inner part of the product.
EP 0 891 769 discloses a solution wherein two different extruders are used for supplying material to a two-layer nozzle. In the two-layer nozzle, the material flow in the inner layer is disrupted by a valve mechanism. So-called encapsulated extrusion products are thus produced wherein the inner material is arranged discontinuously inside the outer material. Disrupting the material flow by the valve mechanism, however, disturbs the operation of the extruder because the extruder is subjected to pressure pulsation. The operation of the extruder is thus disturbed, which means that the product will not be equal in quality.